NOTE: As their name suggests hints are not exactly Above & Below cheats, and are usually just simple (but very useful) tips on how you can unlock secret level, features, find hidden areas and such. Hopefully these will make playing Above & Below even more entertaining.

Achievements
Complete each achievement to receive the allotted gamerscore

Defeat(20): Finish the campaign and get the "Defeat ending".
Done(25): Finish a mission with a 100% enemies destroyed rating.
Double Gun(10): Upgrade your weapon to the 1st level.
Dreadful(20): Destroy 2000 enemies through the entire game.
Experienced Soldier(10): Destroy 100 enemies through the entire game.
Fast(10): Upgrade your weapon to the 2nd level.
Faster(10): Upgrade your weapon to the 3rd level.
Fresh Blood(10): Destroy 50 enemies through the entire game.
Immortal(25): Finish a mission without losing any HP.
Killing Machine(10): Destroy 500 enemies through the entire game.
Legendary(15): Destroy 1000 enemies through the entire game.
Monster(25): Destroy 5000 enemies through the entire game.
New Recruit(10): Destroy 30 enemies through the entire game.
Stunt Pilot(30): Destroy 8 enemies with one barrel roll or loop.
The Back-up Boys(20): Upgrade your weapon to the 4th level.
The Secret Weapon(20): Keep a special ammo up for 60 seconds.
Victory(30): Finish the campaign and get the "Victory ending".
Worth The Cost(10): Destroy 200 enemies through the entire game.